Hmmm, I bought a $100 Murray with a 4.5 hp Briggs and Stratton back in 2003 from Wal-Mart or somewhere and it came with a straight 30 weight recommendation and had the "excessive consumption" warning. I didn't change the oil until 2007. It had never dropped. I believe I replaced it with some older SJ Pennzsoil Synth 10W30. It did, indeed use oil after that. Hmmm, maybe some M1 0W40 for the next fill?
Honestly, I want the mower to die so I can have justification for a nice near rear bagger. But it cranks right up on the first pull every dang time.